ASTRO-PHYSICS German Equatorial 1200GTO User manual

1
ASTRO-PHYSICS
1200 GERMAN EQUATORIAL WITH
GTO SERVO MOTOR DRIVE
For Mounts shipped starting in July, 2007. Beginning with Serial Number 1200723
MODEL 1200GTO PARTS LIST – MODEL GTOCP3 3
FEATURES AND SPECIFICATIONS 4
INTRODUCTION 4
INTRODUCTION 5
Why Polar Alignment is Important 5
ASSEMBLY DIAGRAM 6
BEFORE YOU LEAVE HOME 7
Gross Latitude Adjustment for 1200GTO German Equatorial Mounts 7
Attach Pier Adapter to Pier Post (purchased separately) 9
Standard Pier Adapter (1200SPA) 9
Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (1200RPA) 10
Hi-Lo Latitude Wedge Pier Adapter Assembly (1200WDGA) or Wedge Alone (1200WDG) for 0 - 22°
or 69° - 90° Latitude – North or South 11
AT YOUR OBSERVING SITE 12
Assemble Pier (purchased separately) 12
Assemble Polar Axis Assembly to Pier or Tripod 12
Polar Alignment – Part 1 – Rough Alignment 13
Altitude and Azimuth Adjustments - Rough polar alignment 13
Assemble Declination Axis 14
Removing Declination Axis at the End of your Observing Session 14
Attach Mounting Plate (purchased separately) 15
Attach Counterweight Shaft and Counterweights 16
Attach Mounting Rings and Scope (purchased separately) 16
Polar Alignment – Part 2 - Fine Polar Alignment 16
Methods for fine polar alignment 16
Azimuth Adjustments 17
Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (1200RPA) 17
Standard Pier Adapter (1200SPA) and Hi-Lo Latitude Wedge (1200WDGA) 17
Altitude Adjustment 18
Tips for Adjusting the Altitude 18
Understanding the R.A. and Dec. Clutch Knobs 19
Balancing Your Telescope 19
First, Balance the Declination Axis 19
Second, Balance the Polar Axis 20
SERVO MOTOR DRIVE 21
GTO Control Box – Model GTOCP3 21
R.A. and Dec. Cable Connections 21
12V Connector 21
POWER Indicator Light 22

2
KEYPAD Connector 22
RS-232 Connectors 22
FOCUS Connector 22
RETICLE Connector 23
AUTOGUIDER Connector 23
+6V Connector 23
N and S Switch 23
Drainage Holes 23
Removing the GTO Control Box From 1200 Mount 23
GTO KEYPAD OPERATION 23
PULSEGUIDE BY SIRIUS-IMAGING 23
PEMPRO ASTRO-PHYSICS SPECIAL EDITION BY SIRIUS-IMAGING 24
CABLE MANAGEMENT 25
1200 Motor Cables 25
Accessory Cables 25
Example from International Space Station – Amateur Telescope (ISS-AT) Project 25
SLEWING YOUR MOUNT IN BELOW FREEZING TEMPERATURES 27
MOUNT CARE, CLEANING AND MAINTENANCE 28
Care 28
Cleaning and Touch-up 28
Routine Mount Maintenance 28
ADDITIONAL TIPS AND SUPPORT 28
TROUBLESHOOTING 29
RECOMMENDED READING FROM OUR STAFF 32
STANDARD PIER ADAPTER OF THE 1200 MOUNT 33
CLUTCH PLUG REPLACEMENT FOR 900 OR 1200 MOUNT 34
Construct Your Own Clutch Plug Extraction Tool 35
CHARACTERIZING THE DEC AXIS MOTIONS 36
ASTRO-PHYSICS MOUNTING PLATE FASTENER CHART 37
PLEASE RECORD THE FOLLOWING INFORMATION FOR FUTURE REFERENCE
MOUNT SERIAL NUMBER: ______________________________
KEYPAD SERIAL NUMBER: ______________________________
GTOCP3 SERIAL NUMBER: ______________________________
PURCHASE DATE: ______________________________

3
ASTRO-PHYSICS
1200 GERMAN EQUATORIAL WITH
GTO SERVO MOTOR DRIVE
For Mounts shipped starting in July, 2007. Beginning with Serial Number 1200723
MODEL 1200GTO PARTS LIST – MODEL GTOCP3
1 Polar axis assembly (right ascension-R.A.) with Servo Box GTOCP3
1 Declination (Dec.) axis assembly
1 19.5” (18.5” usable) Stainless counterweight shaft (1.875” dia.) with machined, black-anodized, safety stop
1 Y cable – R.A. portion is 12.5” long and Dec portion is 37.5” long
1 D.C. power cord (cigarette lighter adapter on one end) - 8’ long
1 GTO Keypad controller with 15’ coiled cable, Instruction Manual and installed Keypad Protector (KEYPRO)
1 Hex key set
2 8-32 thumbscrews (substitute these for 8-32 set screws that hold GTO Servo Control Box in place, if you wish)
1 PEMProAP™ Periodic Error Management software for Astro-Physics mounts (CD-ROM)
1 PulseGuide™ by Sirius Imaging – remote control utility for improved guiding (CD-ROM)
In order to fully assemble your mount, you will need the following items sold separately:
•Telescope mounting plate – many choices to fit your telescope and observing needs.
•22° to 69° latitude: choose either the Standard Pier Adapter (1200SPA) or the Precision-Adjust Rotating Pier
Adapter with Azimuth Bearing (1200RPA). Either adapter will come with six 5/16 – 18 X 5/8” button head
screws for attachment to the pier, four pier knobs for attaching the mount to the adapter, and the azimuth block
for use with the Heavy Duty Azimuth Adjuster found on all 1200GTO mounts produced after August, 2005 and
available as an upgrade for earlier mounts.
•Tropical or extreme polar latitudes (0° to 22° or 69° to the pole North or South): choose the Hi-Lo Latitude
Wedge Pier Adapter Assembly (1200WDGA) or the Wedge alone (1200WDG) with Flat Surface Adapter
(1200FSA) and Rotating Pier Adapter (1200RPA)
•10” O.D. pier – Astro-Physics has several heights and styles to choose from.
•Counterweights – 5 lb. (5SCWT), 10 lb. (10SCWT) and 18 lb. (18SCWT) are available.
•Portable rechargeable 12 volt battery pack. Several sizes and types are available from a variety of vendors. Be
sure that your battery pack can supply adequate power for an entire observing session! (see power
requirements under Features and Specifications on next page) We recommend having separate batteries – one
for the mount – one for all other accessories: camera, dew removers etc.
•Regulated Power Supply (110V AC to 12V DC converter) – we offer two choices: 13.8 volt 5 amp supply
(PS138V5A) or 15 volt, 10 amp supply (PS15V10A).
Many of these items will be discussed throughout these instructions. Several additional options are available:
•9” counterweight shaft extension (M12675)
•Santa Barbara Instrument Group CCD Imaging cameras and ST-4 Autoguider or STV - if you plan to pursue
CCD imaging or astrophotography
•Pier accessory trays for 10” pier (TRAY10) and/or Eyepiece Accessory Trays (TRAY10H) and support bars: Bi-
Level (TRAYSB) or Single Level (TRAYSB1) - handy to keep your eyepieces and accessories close at hand
•Polar axis telescope (PASILL4 – Prior versions sold by Astro-Physics will also work.) - threads into the base of
the polar axis assembly. Many users find a polar axis telescope useful for zeroing in on the pole quickly,
particularly with telescopes that are not orthogonal to the mount.
•Extension cable for keypad. Please call Astro-Physics to obtain a quote on the length of extension cable you
need.
Note on Encoders: Mounted shaft encoders can no longer be used with the 1200GTO (for mounts shipped starting in
May, 2006 – beginning serial number 1200572) because of the counterweight shaft re-design. They are not needed
since the go-to functions of the mount are so much more accurate. The encoder that is built into the servo motor itself
has a resolution of 0.05 arc seconds vs. 324 arc seconds for mounted encoders.

FEATURES AND SPECIFICATIONS
R.A. worm wheel: 10.3”, 225-tooth aluminum
Dec worm wheel: 7.2”, 225-tooth aluminum
Worm gear: Brass
R.A. shaft: 3.35” diameter
R.A. thrust bearings: 9.5” diameter
Dec shaft: 2.36” diameter
Dec thrust bearings: 6.5” diameter
Counterweight shaft: 19.5” overall, 18.5” useable length, 1.875” diameter, stainless steel, removable with Safety Stop
Latitude range: 22 - 69 degrees with or without polar scope attached (0 – 90 degrees with optional Wedge)
Azimuth adjustment: Approximately 14 degrees
Setting circles: Porter Slip Ring design, engraved
Right ascension: 4-minute increments, pointer
Declination: 1-degree increments, pointer
Motors: Zero-cogging servo motors
Power Consumption: 0.4 amps at the sidereal rate
3 amps both motors slewing
Power requirements: 12 VDC, range 11.5 to 16V (higher than 12V recommended for very cold temps and heavy loads,
but DO NOT exceed 18V.)
Weight of mount: Equatorial head: 81 lbs. (36.7 kg)
Dec axis: 31 lbs. (14.1 kg)
R.A axis: 50 lbs. (22.7 kg)
Counterweight shaft: 14 lbs. (6.4 kg)
Capacity of mount: Approximately 140 lb. (63.6kg) scope and accessories (not including counterweights), depending
on length. Will accommodate Astro-Physics and similar refractors up to 206mm f8, 16"
Cassegrains and Ritchey-Chretiens.
These are only guidelines. Some telescopes are very long for their weight or heavy for their size
and will require a larger mount.
4

INTRODUCTION
The 1200 German equatorial was designed to meet the needs of the advanced observer who requires a mount with
maximum strength and rigidity and minimum weight. The excess material in both axes has been carved out while retaining a
heavily ribbed structure for internal strength and rigidity. A unique dovetail was machined into the mating surfaces of the R.A.
and Dec axes. This feature allows quick and easy assembly in the field without any tools.
The DC servo motor drive with GTO computer system, the keypad with its digital display screen, and the included
PulseGuide™ and PEMProAP™ software all combine to offer extraordinary sophistication for today’s observer. Whether you
enjoy visual astronomy exclusively or plan an aggressive astrophotography or CCD imaging program, this mount will allow
you to maximize your night out under the stars.
The advanced keypad features allow you to slew automatically to objects in a wide range of databases as well as any
R.A./Dec coordinate. A large selection of common names for stars and other objects makes your selection a snap. The rapid
slew rate of 5 degrees per second (1200x) allows you to locate objects very quickly and accurately. You will be very pleased
with the intuitive operation of this keypad. There are no complicated sequences of keystrokes to remember. It is so easy to
use that even if you don’t use it for a few months, you will feel at home with the keypad very quickly.
PulseGuide™ is a stand-alone Windows (98, ME, 2000, NT4, XP, Vista) utility that provides complete remote control of all
Astro-Physics GTO mounts. It derives its name from its most distinctive feature, pulse guiding, which can improve unguided
tracking. Specifically, it can help correct tracking errors caused by polar misalignment and atmospheric refraction. You can
also train PulseGuide™ to track objects moving relative to the stars, such as asteroids, comets, and the moon. In addition to
pulse guiding, PulseGuide™ also has many useful utility features. PulseGuide™ was written by Ray Gralak of Sirius-
Imaging. Please refer to his website http://www.pulseguide.com for further developments and enhancements.
PEMPro™ (Periodic Error Management Professional) is a Windows software application that makes it easy to characterize
and reduce periodic error. PEMPro™ will analyze the performance of any mount that is equipped with a CCD camera and
compatible camera control software. PEMPro™ gives you powerful tools to program your mount's periodic error correction
firmware to achieve the best possible performance for your mount. PEMPro™ dramatically improves guided and unguided
imaging resulting in better images and fewer lost exposures. PEMProAP™ is a special edition that can only be used with
Astro-Physics mounts. While the native periodic error of your 1200GTO will be 5 arc seconds or less, you can reduce it even
further to maximize performance without auto-guiding. PEMProAP™ is included with all 1200GTO mounts that will ship in
2007. As an added bonus, starting in 2007, all 1200GTO mounts will come pre-loaded with the custom fitted PEMPro
corrections from our extensive individual testing that is performed on each and every mount.
The 1200 is equally at home in a permanent observatory or as a portable mounting for remote star parties thanks to the ease
with which the two axes come apart. This is the perfect mount for a large refractor, Newtonian, Cassegrain or astrograph.
In order to maximize your pleasure on your first night out, we
recommend that you familiarize yourself with the assembly
and basic operation of the mount indoors. The temperature
will be comfortable, the mosquitoes at bay, and you'll have
enough light to see the illustrations and read the manual.
Please take particular note of counterbalancing, use of the
clutches and operation of the keypad controller.
Why Polar Alignment is Important
Polar alignment compensates for the Earth’s rotation.
If you were to take a long exposure photograph with Polaris
(often called the north star) in the center of the field, you
would discover that all stars seem to revolve around Polaris.
This effect is due to the rotation of the earth on its axis.
Motor-driven equatorial mounts were designed to
compensate for the earth's rotation by moving the telescope
at the same rate and opposite to the earth's rotation. When
the polar axis of the telescope is pointed at the celestial pole
(polar aligned) as shown in the diagram at right, the mount
will follow (track) the motions of the sun, moon, planets and
stars. As a result, the object that you are observing will
appear motionless as you observe through the eyepiece or
take astrophotos.
5

ASSEMBLY DIAGRAM
Please read all instructions before attempting to set up your 1200 mount. The Model 1200 is very rugged, however like any
precision instrument, it can be damaged by improper use and handling. Please refer to the diagram below for an illustration
of the mount. The parts are labeled so that we can establish common terminology.
The following terms and abbreviations are used interchangeably in these instructions:
polar axis = right ascension axis = R.A. axis = R.A. housing
declination axis = dec. axis = dec. housing
Your 1200GTO must be used with a pier adapter which includes the azimuth adjuster block, center pivot screw and pier
adapter knobs. Please choose one as shown below.
203040
50
60
7080
90
80
70
Counterweight
(optional)
Counterweight
knob
Counterweight
shaft
Declination axis housing
Sight hole cover
Dec. Cable connector
Dec. Motor
/
gearbox housing
Dec. Clutch knobs (4)
Dec.
Lock
knob (2)
R.A. Clutch knobs (4)
Right ascension axis housing
Control box
(GTOCP3)
Altitude locking knob
Polar axis pivot screw
Altitude adjustment knob Altitude adjustment position hole
s
Tommy bar
Polar Fork
Base assembly
Azimuth adjustment knob
1200 Precision-Adjust Rotating Pier Adapter
with Azimuth Bearing (1200RPA)
(optional)
1200 Standard Pier Adapter (1200SPA)
(optional)
Azimuth adjustment Block
5/16-18 x 5/8” buttonhead screws (6)
5/16” x 9/16” O.D. x .060” washer (6)
R.A. axis rear cover
Safety Stop
R.A. Setting circle
Dec. Setting circle
Pier Adapter Knob
with Washer (4)
1200 Hi-Lo Latitude Wedge
Assembly (1200WDGA)
(optional)
6

BEFORE YOU LEAVE HOME
Since most of us must set up our instruments in the dark, in the cold or while battling mosquitoes, a bit of pre-planning and
organization is important. There are few simple things that can be accomplished in the comfort of your home before heading
outside.
Gross Latitude Adjustment for 1200GTO German Equatorial Mounts
Mounts shipped starting in May, 2006. Beginning with Serial Number 1200572
NOTE: Older mounts will have slightly different latitude ranges.
The latitude range of the 1200 mount is approximately 22 - 69 degrees with considerable overlap at each position. Since
most astronomers typically observe within one latitude range, this adjustment is made just once, if at all. Prior to shipment,
we preset the mount to your latitude range for your convenience. We suggest that before you travel to an observing location,
determine the approximate latitude of your observing site and make the appropriate rough adjustment. If you live in or plan to
travel to locations that are 0-22 degrees latitude, we recommend our Hi-Lo Latitude Wedge Assembly (1200WDGA).
The four positions for the altitude adjustments have the following approximate ranges:
57.5° to 69° latitude - top position (1)
41° to 63° latitude - second position (2)
30° to 48.5° latitude - third position (3)
22° to 38° latitude - bottom position (4)
How to change the position of the altitude adjuster
1. Use only the R.A. axis. DO NOT attempt
to make these adjustments with the
declination axis in place and certainly not
with an instrument fully mounted.
2. Loosen both altitude-locking knobs about
1 turn.
3. Locate the side of the polar axis that
does not have the motor / gearbox
housing. Loosen (about 1 turn) the polar
axis pivot screw and altitude adjuster bar
fixing screws on this side only. With your
hand, push the polar axis upwards so
that the altitude-locking knobs are
positioned at the top of the altitude slot
(this is the maximum altitude position).
Some resistance will be felt with this
operation as you are pushing against the
weight of the polar housing and the
resistance of the remaining polar axis
pivot screw (which has not been
loosened).
4. Before attempting to remove or move the altitude adjuster bar, you must
tighten the altitude-locking knob on the motor / gearbox housing side.
This will prevent any downward movement of the polar axis during
positioning of the altitude adjuster bar.
AB
CDE
Front
(North)
A
B
CD
E
A is the
Latitude
Hole
5. While supporting the altitude adjuster bar, remove the two screws that
support it on each side (4 screws in all). Keep the two ends of the bar in
contact with the side of the mount, don't remove the bar completely (this
tip is for your convenience).
6. Determine the latitude range that you need and position the altitude
adjuster bar so that the hole that is marked “A”, as shown in the diagram,
is located at the appropriate hole position numbered 1-4 in the diagrams
(above and next page). Note that hole “A” is located at the rounded part
in the center of the altitude bar. Hole “A” is the “latitude hole.”
7. Attach two of the screws (one on either side of the adjuster bar) through
the appropriate altitude adjustment position hole and into hole A of the
7

adjuster bar, but do not tighten. Rotate the
altitude adjuster bar around this pivot point
until the corresponding hole lines up.
Consult the diagram to determine which
hole of the altitude adjuster bar should be
used. Be very careful since the holes
marked C and D are very close to one
another. The incorrect hole may appear to
line up, however it will be slightly off. If you
try to attach at the incorrect hole, you may
strip the threads of the altitude bar. The
correct hole will orient the adjuster to be
roughly perpendicular to the axis once the
axis is lowered into place.
Altitude Adjuster Bar
Polar (R.A.)Axis
Housing
Altitude Adjustment
Knob
Azimuth Adjustment
Knobs
Azimuth Adjuster
Tommy Bar
Azimuth Adjustment Block
(partly hidden)
Shown with Optional
Pier Adapter
North Pier Knob Removed
for clarity
Altitude Adjuster Bar
Fixing Screws
Altitude Adjuster Bar
Fixing Screws
8. Once you have located the correct hole,
insert the remaining two screws, and lightly
tighten so that you still have some ability to
wiggle the bar.
9. Note that the altitude adjustment knob is attached to a
threaded rod that travels through the altitude adjuster bar.
Turn the knob so that the altitude adjuster bar is positioned
approximately in the middle of the threaded rod. You should
see about half of the threaded rod protruding from both sides
of the altitude adjuster bar. This will allow you to move the
mount fully within the altitude range.
22º - 38º
B = 3
A = 4
30º - 48 º
C = 4
½
A = 3
41º - 63º
D = 3
A = 2
(SHOWN SETTING)
57 ½ º - 69º
E = 2
A = 1
1
2
3
4
10. At the end of the threaded rod mentioned in the last step, you
will see a small brass altitude adjuster thrust pad. This is the
part that will come in contact with the polar axis as you ease it
back into position. Loosen the altitude-locking knob
(motor/gear side) and lower the polar axis so that it rests
comfortably on this pad. The threaded rod should be
positioned at roughly a right angle to the polar axis housing.
Firmly tighten the altitude adjuster bar fixing screws.
11. Turn the altitude adjustment knob to raise or lower the polar
axis to your approximate observing latitude. Tighten the
altitude locking knobs with finger pressure only. You do not
need to tighten with the hex key.
12. Firmly tighten
both polar axis pivot screws with the hex key.
8

Attach Pier Adapter to Pier Post (purchased separately)
If you purchased the pier from Astro-Physics, the pier adapter of the 1200 will attach right to the top of the pier. If you are
constructing your own pier or tripod, you will need to incorporate this part. Three models of the pier adapter are now available
for use with the 1200 from Astro-Physics. The Standard Pier Adapter (1200SPA) and the Precision Adjust Rotating Pier
Adapter (1200RPA) are the choices for people living within the mount’s 22 to 69 degree latitude range. For customers in
tropical or extreme polar latitudes, the third adapter: the Hi-Lo Latitude Wedge is also available as either a complete
assembly (1200WDGA) or as the Wedge alone (1200WDG). If you have more than one pier, you may wish to purchase two
adapters so that you can leave them attached permanently. You will probably want to attach the pier adapter to the pier post
before going to your observing site. We recommend that you leave whichever pier adapter you choose attached to your pier
post for transport and storage. These pier adapters can be used with all prior versions of the 1200 mount.
If you did not purchase one of our pier adapters described below - for instance, if you purchased the Monolith Pier from
Particle Wave Technologies, you will need to purchase the Pier Adapter Knob Kit (part# 12KBKIT) in order to attach your
mount to the Monolith.
Important notes for all three pier adapters or when using the Monolith
Pier :
•The washers for the pier adapter knobs must be positioned with the
smooth surface and rounded edge down so that the assembly can
be adjusted back and forth. (Not important for the Precision-Adjust
Rotating Pier Adapter.)
•Do NOT remove the center pivot screw. Just as the name implies,
this is the point around which the mount rotates (pivots) when
making azimuth adjustments. The screw head has been machined
to assure a close fit. Please do not replace it with another screw.
Standard Pier Adapter (1200SPA)
This 1200 Pier Adapter is similar to those that we have included with mounts in the past, however the azimuth adjuster block
is slightly taller to accommodate the improved azimuth adjuster assembly on all 1200GTO mounts produced after January,
2004 (and all upgraded older mounts). If you have a permanent installation, this base is a good choice since you will not have
to set up every session.
The adapter includes the machined flat plate, four machined aluminum lock knobs with 5/16 " ID x 1.5" OD stainless
washers, the azimuth adjuster block, center pivot screw and six 5/16-18 x 5/8 button head screws and washers. All
machined parts are black anodized. The Standard Pier Adapter was designed to fit into a 10" x 0.094" wall tube.
Attach to an Astro-Physics pier: To attach the pier adapter to your Astro-Physics pier, simply
set the adapter into the top of the pier post, make sure the azimuth adjuster block is on the
north side, and fasten from the side with the six screws and washers provided.
Attach to a flat surface on your own pier: If you are mounting to a flat surface of your
own design, simply use four 1/4–20 stainless steel cap screws of appropriate length,
fastened through the top of your adapter. Refer to the diagram in the back of the manual
for bolt pattern information.
If you prefer a more finished look, you may wish to consider using our 1200 Flat Surface Adapter (1200FSA). The Flat
Surface Adapter bolts onto the flat plate on top of your pier or tripod, then the Standard Pier Adapter slips in (just as it fits into
our pier) and you fasten from the side with the six screws and washers provided with the Standard Pier Adapter. The bolt
circle for attaching the 900 Flat Surface Adapter to your pier is 7.230” diameter.
Using an ATS pier:The O.D. of the plate will need to be modified by ATS for an additional charge.
9

Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (1200RPA)
This pier adapter was designed for very accurate and smooth adjustment of the azimuth angle without loosening the lock-
down knobs on the base of the mount. The top plate of the adapter rotates through the 1200GTO mount’s full 14 degrees of
azimuth motion. (It does not rotate through a full 360 degrees!) This Precision-Adjust Rotating Pier Adapter is the ideal
choice for portable setups as it makes azimuth adjustment so easy. Upgrade your previous model 1200 mount (any version)
and enjoy the ease of use. Do a setup, followed by a fine polar alignment at a remote site just once, and you will wonder
how you ever got along without this pier adapter!
The adapter includes the flat plate assembly, four machined aluminum lock
knobs with 5/16 " ID x 1.5" OD stainless washers, a tall version of the azimuth
adjuster block, center pivot screw and six 5/16-18 x 5/8 button head screws and
washers.
Attach to an Astro-Physics pier: Simply fit the Precision-Adjust Rotating Pier
Adapter into your Astro-Physics Portable Pier just like the Standard Pier
Adapter and fasten it from the side with the six screws and washers
provided. Again, make sure that the Azimuth Adjuster Block is on the north
side.
Attach to a flat surface on your own pier: The Precision-Adjust Rotating Pier
Adapter must fit inside another part and be bolted from the side. It cannot be
bolted through the top as you can with the Standard Pier Adapter. We
recommend our 1200 Flat Surface Adapter (1200FSA). The Flat Surface
Adapter bolts onto the flat plate on top of your pier or tripod, then the
Precision-Adjust Rotating Pier Adapter slips in (just as it fits into our pier)
and you fasten from the side with the six screws and washers provided with
the Precision-Adjust Rotating Pier Adapter. The bolt circle for attaching the
1200 Flat Surface Adapter to your pier is 9.230” diameter.
Using an ATS pier:If you plan to use an ATS pier, the O.D. of the plate will
need to be modified by ATS for an additional charge.
The two recessed screws (3/16 hex), shown by the arrows, adjust the
tension between the two plates of the Precision-Adjust Rotating Pier
Adapter. These are preset to an optimal tension and should rarely, if ever,
need to be re-adjusted. You do not need to tighten or loosen these two
screws as part of your normal polar alignment routine.
10

Hi-Lo Latitude Wedge Pier Adapter Assembly (1200WDGA) or Wedge Alone (1200WDG) for 0 - 22°
or 69° - 90° Latitude – North or South
If your latitude is between 22° north and 22° south or above 69°, either north
or south, this wedge assembly includes everything you need to place your
1200 mount in the proper position.
The 1200 Wedge Assembly includes the machined wedge and flat plate, the
1.2" Azimuth Adjuster Block, four Pier Adapter Knobs with 5/16" ID x 1 ½" OD
flat washers, the center pivot screw, six 5/16-18 x 5/8 socket button head
screws and six 5/16 x 9/16"OD x 0.060" flat washers, which enable you to
attach the pier adapter to your Astro-Physics pier.
Please Note: The photo shows the Hi-Lo Latitude Wedge
ready to be used at tropical latitudes with the Azimuth Adjuster
Block on the low side. For extreme polar latitudes, the
Azimuth Adjuster Block can simply be moved to the high side
of the wedge to extend the useful range of your 1200GTO
above 69° latitude. All required tapped mounting holes are
provided.
Attach to an Astro-Physics pier: To attach the Hi-Lo Latitude Wedge to your Astro-Physics pier, simply set the adapter into
the top of the pier post, make sure the azimuth adjuster block is on the pole side, and fasten from the side with the six screws
and washers provided.
Attach to a flat surface on your own pier: The Hi-Lo Latitude Wedge must fit inside another part and be bolted from the side.
It cannot be bolted through the top as you can with the Standard Pier Adapter. For custom installations, we recommend our
1200 Flat Surface Adapter (1200FSA). The Flat Surface Adapter bolts onto the flat plate on top of your pier or tripod, then
the Hi-Lo Latitude Wedge Pier Adapter slips in (just as it fits into our pier) and you fasten from the side with the six screws
and washers provided. The bolt circle for attaching the 1200 Flat Surface Adapter to your pier is 9.230” diameter.
Using an ATS pier:The O.D. of the plate will need to be modified by ATS for an
additional charge.
More Options: If you already own a 1200Standard Pier Adapter, or if you would like
to construct a “Precision Adjust Rotating Wedge,” you can simply order the 1200
Wedge by itself (It will come with the six 5/16-18 x 5/8 socket button head screws
and six 5/16 x 9/16"OD x 0.060" flat
washers). To use the wedge in place of
a Standard Pier Adapter, simply transfer
the knobs, Azimuth Adjuster Block and
Center Pivot Screw to the Wedge. To
create the “Rotating Wedge,” mount a
1200 Flat Surface Adapter (1200FSA)
onto the top of the wedge using the holes
provided, and then insert a Precision
Adjust Rotating Pier Adapter (1200RPA).
11

AT YOUR OBSERVING SITE
Assemble Pier (purchased separately)
Begin by assembling the portable pier at the desired observing
location. Take note which direction is north.
1. Slide the three legs onto the nubs of the base and
rotate the assembly so that one of the legs points
toward north (or south, if that is your preference).
2. Place the pier post on the base orienting the center
azimuth block directly north. If you choose to have one
leg north, then the pier adapter plate will have to be
installed with the azimuth block directly over a
turnbuckle. If you have one leg south, the pier adapter
plate will have to be installed with the azimuth block
over and between two of the pier post turnbuckles.
3. Attach the tension rods. The turnbuckles should be
drawn tight until the whole assembly is stiff enough to
support your weight without movement.
Assemble Polar Axis Assembly to Pier or Tripod
In order to track the motion of astronomical objects, the polar axis must be positioned so that an imaginary line drawn
through the center of the axis points toward the celestial pole. Refer to the diagram at the front of this manual for a graphical
representation. At this stage of the assembly process, you want to position the mount so that it points roughly north.
1. Remove the four (4) pier adapter knobs from the Pier Adapter and keep them close at hand.
2. Prior to lifting the polar axis assembly into place, turn the fine azimuth adjustment knobs so that the space between
them is wide enough to allow the pier adapter’s azimuth block to fit easily between them. Ensure both pier top and
polar axis assembly mating surfaces are clean and free of dirt. If you are using the Precision-Adjust Rotating Pier
Adapter, make sure that the Altitude Adjuster Block is centered in the slot of the top plate.
3. Place the polar axis assembly onto the pier top
adapter so that the center azimuth block fits
between the fine azimuth adjustment knobs. The
Center Pivot Screw on the Pier Adapter (all models)
will help you center the mount on the adapter.
4. Move the base of the polar axis assembly so that
the threaded holes of the pier top can be seen
through each of the four slots.
5. Thread the four hand-knobs loosely in place (you
will tighten these later after polar alignment) with
the washers underneath. If you are using the
Standard Pier Adapter, be sure that the side with
the rounded edge is facing down. This will ensure
smooth movements as you adjust your polar
alignment. The position of the washers does not
matter for the Precision-Adjust Rotating Pier
Adapter.
12

Polar Alignment – Part 1 – Rough Alignment
We recommend that you accomplish your polar alignment in two phases – rough alignment and fine alignment.
Altitude and Azimuth Adjustments - Rough polar alignment
For rough polar alignment, your goal is to sight the celestial pole when looking through the polar alignment sight hole in the
center of the polar axis. You will need to make altitude (up/down) and azimuth (side-to-side) adjustments to the position of
the mount.
We recommend that you do your rough polar alignment with the
R.A. axis only since you will be making major adjustments to the
position of the mount at this time. The remainder of the mount,
telescope and counterweights will add considerable weight and
require more hand effort. Later, you will do your final polar
alignment with the telescope and counterweights attached, but the
adjustments will be small.
1. If the Polar Scope (PASILL4) is installed, you may
remove it to complete these steps. Alternatively, you can
simply sight up the side of the polar axis to see Polaris.
2. If you examine the polar axis assembly, you will see that
the center of the R.A. shaft is hollow. If you have the
Standard Pier Adapter or the Hi-Lo Latitude Wedge Pier
Adapter and have not done so already, slightly loosen (1/2
turn) the four pier knobs. If you have the Precision-Adjust
Rotating Pier Adapter you do NOT loosen the Pier Knobs.
NOTE: If you have already attached the Dec. axis, remove
the sight hole cover and rotate the internal Dec. shaft by
moving the top of the Dec. axis (or the cradle plate if it is attached) to reveal the sight-hole that has been drilled into it.
Now, you can look through the shaft to the other side.
3. Azimuth adjustments: To begin with, move or turn the entire pier or tripod east or west until the mount is oriented
approximately towards the pole (an imaginary line drawn through the hollow shaft). Use the two fine azimuth
adjustment knobs, one on each side of the mount, to make adjustments. You must back off the opposing azimuth
knob in order to move the other knob in that direction. Please refer to the photos below. These photos also illustrate
the 14 degrees of azimuth adjustment possible with this mount.
One full turn of the azimuth knob is approximately 0.53 degrees (31.8 arc minutes). Small
graduations are 1.06 arc minutes; long graduations are 5.3 arc minutes
4. Altitude (latitude) adjustments: Loosen the altitude locking knobs. Move the polar axis up or down with the large
altitude adjustment knob located in the front of the polar axis assembly. The tommy bar can be positioned in any of
the threaded holes located in the altitude adjustment knob. Use this bar to help you turn the knob. We have found that
using the turnbuckle on the north leg of our pier also can make fine altitude adjustments, if used.
One turn of the altitude knob is approximately 0.5 degrees (30 arc minutes).
5. Continue your azimuth and altitude adjustments until you can sight Polaris in the polar alignment sight hole. At this
point, you have achieved a rough polar alignment, which may be sufficient for casual visual observations, if you are
not planning to slew to target objects with the keypad. When the R.A. motor is engaged (the power is plugged in), it
will compensate for the rotation of the earth and keep the target object within the eyepiece field of view. Your target
object will slowly drift since polar alignment at this stage is only approximate. However, you can make corrections with
the N-S-E-W buttons of your keypad controller.
13

6. Tighten the altitude locking knobs by hand.
7. If you are using the Standard Pier Adapter or the Hi-Lo Latitude Wedge, tighten the pier knobs firmly by hand. On
the Precision-Adjust Rotating Pier Adapter, the knobs will already be tight.
Assemble Declination Axis
A
BB
CC
B
B
D
E
EE
E
A - Single Pocket
B - Dovetails
C - Parallel Guides
D - Altitude Adjuster
Knob
E - Clutch Knobs
R.A. Axis Dovetail
1. Do not have your telescope or counterweights
connected to the Dec. axis assembly for either assembly
or disassembly of the Dec. and RA axes.
2. Position the R.A. axis as shown in the illustration at
right with the single pocket "A" at the top, opposite the
altitude adjuster knob. Firmly tighten R.A. clutch knobs.
3. During shipment, the Dec. axis assembly lock knobs
will be fully screwed into the Dec. axis. For correct
assembly, these lock knobs should be unscrewed at
least 7 full turns and no more then 8.5 full turns. This is
between 5/16" and 3/8" out from the "shipped" tightened
position.
Note: These lock knobs can be completely removed
from the Dec. axis assembly with about 9.5 full turns out.
4. Position the Dec. axis above the R.A. axis as shown
in the lower illustration at right, a light movement
(wiggle) in the downward direction (arrow "A") will help to
correctly seat the principle dovetail(s) and parallel
guides.
5. When both Dec. and R.A. assemblies are fully
seated, hand tighten both Dec. lock knobs.
6. Thread the counterweight shaft into the Dec. axis.
7. Remove the Safety Stop from the base of the
counterweight shaft. Add sufficient counterweights (10 or
18 lb. counterweights are purchased separately) to the
declination shaft to balance the telescope you intend to
use. Always use two hands to attach or move them on
the shaft.
8. Reattach the Safety Stop to the end of the declination
shaft. This will help to prevent injury if someone
accidentally loosens the counterweight knob.
NOTE: Firm tightening of the counterweight knob will not
damage the surface of the counterweight shaft. The pin
that tightens against the stainless counterweight shaft is
constructed of brass. Likewise the bronze sleeve that
has been press fit into the center of the counterweight
will prevent marring of the shaft as you move the
counterweight up and down.
Removing Declination Axis at the End of your
Observing Session
1. Remove your telescope, counterweights and
counterweight shaft.
2. Unscrew the lock knobs 5.5 to 7 full turns (this is still 5/16" to 3/8" out from the fully tightened position) and slide/tilt
the Dec. axis assembly in an upwards direction (arrow "B").
3. For transport/storage we recommend fully tightening the lock knobs.
14

Attach Mounting Plate (purchased separately)
Several mounting plates (also called cradle plates) are available for the 1200 mount. If you own more than one instrument,
you may need more than one plate. Follow the appropriate directions for the plate(s) that you have. The darkened holes
represent those used for the 1200 mount.
18" FLAT MOUNTING PLATE (FP1800)
This plate is 18" long and 7.5" at its widest point in the center. The width
of the plate tapers to 5.5" at each end. Four pairs of keyhole slots that
measure 3.2" between centers are provided. The two inner pairs are
13.75" apart and the outer two pairs are 17" apart. You can drill
additional holes to suit your needs. This plate also fits the 900 German
Equatorial.
Attach this plate with six 1/4-20 x 1" flat head socket cap screws
15” RIBBED MOUNTING PLATE (1200RP15)
This plate is 14.75” long, 7.75” at its widest point, 5” at each end and 1” thick. The
underside of the plate is carved into a ribbed pattern to maximize the strength and
minimize the weight - 3 lbs. A pair of keyhole slots that measure 3.2” between
centers are provided at each end. The distance between the pairs is 13.75”.
Attach this plate with six 1/4-20 x 3/4“ socket head cap screws Note that the plate
is asymmetrical. In most cases, orient the plate so that the long end points toward
the sky. You can also turn the plate in the other direction to balance your scope.
24" RIBBED MOUNTING PLATE (1200RP)
For larger instruments, the ribbed structure of this plate
provides the maximum support. Our machinist begins with
thick aluminum plate and carves a strong rib structure. The
final result is 1.5" thick, 24" long and 7.6" at its widest point.
The width of the plate tapers to 5.5" at each end. A pair of
keyhole slots that measure 3.2" between centers are provided
at each end. The distance between these pairs of holes is
23". Due to the ribbed structure, you may not be able to drill
additional holes for non-Astro-Physics mounting rings. The
plate weighs an amazing 9.5 lbs. for its size. This is a view of
the rib structure on the underside of the 24" plate.
Attach this plate with six 1/4-20 x1" socket head cap screws.
8.5” DOVETAIL FOR LOSMANDY D SERIES PLATE (DOVELM2)
This Astro-Physics plate attaches to the 400, 600E, 900 and 1200 mounts. If you already own one of
the Losmandy DAP series (fits Astro-Physics refractors), DC series (for Celestron 8" 9.25” or 11"
SCTs) or DM series (for Meade 8" and 10" SCTs) plates, you should consider this plate or the longer
DOVELM16. For larger size SCT’s we recommend the longer DOVELM16 – see below.
Note that the bolt-hole pattern is offset from the center. This allows you to position the plate either
forward or backward depending on the balance point of your telescope. Attach this plate with four 1/4-
20 x 3/4" socket head cap screws and/or two 1/4-20x5/8" flat head socket cap screws.
16" DOVETAIL FOR 1200 MOUNTS AND LOSMANDY D SERIES PLATES (DOVELM16)
This Astro-Physics plate attaches to the 1200 mount. If you already own one of
the 17.25” or longer Losmandy DAP series (fits 6” and larger Astro-Physics
refractors), DC series (for Celestron 11" or 14" SCTs) or DM series (for Meade
10", 12" and 14" SCTs) plates, this is the mounting plate for you.
Note that the bolt-hole pattern is offset from the center. This allows you to position
the plate either forward or backward depending on the balance point of your
telescope. Attach this plate with 1/4-20 x 1" socket head cap screws.
15” ASTRO-PHYSICS DOVETAIL (DOVE15) FOR 15” SLIDING BAR (SB1500)
The 15" version of our dovetail plate is suited for the 130 f8 StarFire EDT, 155 f7
StarFire EDFS, ARO Maksutovs, Takahashi scopes and other instruments of similar
size. The knob assembly features a brass pin with a tapered end to hold your sliding
bar firmly without marring the aluminum. Use with the 15" Sliding Bar (SB1500),
which is sold separately (NOT for use with Losmandy “D” plates). Also makes a
great accessory plate when used with either the 1200RP15 or FP1800 (with rings
mounted to inside holes)
Attach with four 1/4-20 x 5/8 flat head socket cap screws.
15

Attach Counterweight Shaft and Counterweights
IMPORTANT:
•Always attach the counterweights before mounting the telescope to the cradle plate to prevent sudden
movement of an unbalanced tube assembly, which may cause damage or injury.
•Remember counterweights are heavy and will hurt if they fall on your foot.
1. Thread counterweight shaft onto the Dec. axis. Be careful not to cross-thread! Do not tighten too much, since
you will need to remove it later.
2. Remove the safety stop (a hand knob and washer were provided on older mounts) from the end of the
counterweight shaft. Add sufficient counterweights (5, 10 or 18 lb. counterweights are available) to the shaft to
balance the telescope you intend to use. Loosen the counterweight knob and hold the counterweight with the knob
pointing downward so that the brass pin will move from the center opening allowing the counterweight to slide into
position. Always use two hands to attach or move them on the shaft. It is advisable to have the counterweight
knob pointing down toward the pier. This will minimize the chance of accidentally loosening the counterweight
during the observing session.
3. Re-attach the safety stop to the end of the counterweight shaft. This will help to prevent injury if someone
accidentally loosens the counterweight knob.
A firm tightening of the counterweight knob will not damage the surface of the counterweight shaft. The pin that tightens
against the stainless counterweight shaft is constructed of brass. Likewise, the bronze sleeve that has been press fit into the
center of the counterweight will prevent marring of the shaft as you move the counterweights.
Attach Mounting Rings and Scope (purchased separately)
Flat and ribbed plates: Our flat and ribbed plates are constructed with keyhole slots at the location where your mounting
rings attach. This feature enables you to partially loosen the screws on your rings just enough to insert them into the larger
part of the keyhole, then slide the rings to the narrow part and tighten them with a hex key. We prefer this keyhole method to
the standard way of completely removing the screws and dropping them in the grass.
We suggest that you install the rings on the mounting plate, then open the rings, lift the scope in place, close the rings and
tightened the knobs. To balance the scope, you can loosen the knobs enough to slide the scope forward or backward as
needed.
Another approach is to attach the rings to the scope beforehand, then lift onto the mounting plate, However, the rings must
be spaced exactly the correct distance apart to match the holes in the plate. This maneuver may be particularly difficult to
accomplish with a large, heavy instrument.
Dovetail plates or sliding bars: Attach mounting rings to the male dovetail plate (sliding bar) matching the appropriate
threaded holes on the bottom of the mounting ring. Again, you have the option of attaching this dovetail/ring assembly to the
mount and then lifting your scope in or placing the scope in the rings, then lifting the entire assembly to the female mounting
plate already attached to the mount. Dovetail plate / sliding bar combinations are quick, versatile and convenient – hence
their popularity. Simply loosen the knobs and “tilt” the sliding bar into place in the dovetail receiver. Once in place, tighten
the knobs to lock everything securely. Loosen the knobs and slide the scope / rings / sliding bar assembly in the dovetail
channel as needed to balance the system, and then re-tighten when balanced.
Polar Alignment – Part 2 - Fine Polar Alignment
If you plan to use any of the go-to functions of the 1200GTO or do astrophotography, you must polar align. Procedures will
be discussed here, however you will complete this alignment when your scope and other equipment are mounted.
Methods for fine polar alignment
•Polar Alignment Scope – Our optional polar scope (PASILL4 or earlier models) will allow you to quickly align your
mount on the pole stars. The reticle was designed for use in both the Northern and Southern hemispheres. Even
users of the GTO computerized mounts will find these polar scopes useful, particularly if your telescope is not
orthogonal to the mount (please refer to the keypad manual for a discussion of orthogonality). If you have a polar
alignment scope, please read the instructions sheets that come with it. If you are planning long exposure
astrophotos or imaging, we suggest that you use the polar axis telescope, then tweak the final polar alignment by
using the GTO keypad and, perhaps, CCDOPS from SBIG (discussed below) or other similar alignment program.
16

•GTO Keypad – Please refer to the instruction manual for the GTO Keypad and read the section describing the
startup sequence and various polar alignment procedures including a procedure you can do in the daytime.
•CCDOPS - We suggest that you refer to detailed instructions in the GTO Keypad manual for a method that utilizes
CCDOPS from Santa Barbara Instrument Group (SBIG) for precise polar alignment. There are also other similar
alignment procedures, including one in MAXIM DL from Diffraction Limited.
•Star Drift method – Traditionally, this has been regarded as the most accurate method of polar alignment.
However, if you are using the old method of drift alignment (star near eastern horizon, etc), you are doomed to
failure. To obtain more accurate results, choose stars somewhere near the celestial equator due south or slightly
east and west, but not below 45 degrees elevation. If you attempt to drift align below that, you will encounter
atmospheric refraction, which skews your alignment.
•Members of the ap-gto Yahoo group occasionally discuss alternative methods of polar alignment that they have
found helpful. We suggest that you participate in this Internet discussion group. Follow the links from the sidebar of
our website to find the group.
Azimuth Adjustments
The one-piece Azimuth Adjustment assembly makes for easy and accurate polar alignment in your observatory or in the
field. The heavy-duty construction and integrated one-piece design results in smooth control of the azimuth axis. Large left
and right adjuster knobs are graduated for precise control of azimuth position angle. The small graduations are 1.06 arc
minutes per graduation; long graduations are 5.3 arc minutes per graduation; one full turn is 31.8 arc minutes or .53
deg. The size of the knobs makes them easy to turn with very little torque required, even with the mount fully loaded.
The procedure for making azimuth adjustments is somewhat different with the Precision-Adjust Rotating Pier Adapter
(1200RPA), Standard Pier Adapter (1200SPA) and Hi-Lo Latitude Wedge Assembly (1200WDGA). If you are using your own
pier adapter or one provided with the Particle Wave Technologies Monolith Pier, there may be additional considerations to
achieve smooth, accurate adjustments.
Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (1200RPA)
The Precision-Adjust Rotating Pier Adapter consists of two plates that allow ultra-smooth adjustments for critical polar
alignment. When using the Precision-Adjust Rotating Pier Adapter, tighten the pier knobs fully by hand. It is not necessary
to use a wrench. These will remain tight during and after the adjustment procedure. Also please note that the altitude axis
should be fully locked down with a hex key before adjusting the azimuth.
Notice the two setscrews on the side of the Precision-Adjust Rotating Pier Adapter. These setscrews are used to apply
tension to the rotating plate. You may on rare occasions need to adjust these setscrews to gain the proper feel during the
adjustment process. If you notice a slight amount of shift, particularly with a larger scope, tighten the screws. If you find too
much resistance, the screws may need to be loosened slightly.
Azimuth adjustment is accomplished with the two fine azimuth adjustment knobs, one on each side of the mount. You must
back off the opposing azimuth knob in order to move the other knob in that direction. Please refer to the illustration on p. 12.
Do not leave the knob you have backed off loose. It must be gently “snugged” against the azimuth adjuster block to hold the
azimuth angle you have set. Follow one of the alignment methods discussed above in the Polar Alignment section.
Once your azimuth position has been attained, do not tighten the hand knobs any further since this is likely to disturb your
alignment.
Standard Pier Adapter (1200SPA) and Hi-Lo Latitude Wedge (1200WDGA)
Each of the azimuth lockdown knobs has a hardened washer. With these washers, the lockdown knobs can hold the mount
down tight while still allowing the axis to be easily adjusted with your fingers. These will eliminate minor shifts in the axis
when you are tweaking your azimuth adjustment.
The washers have a sharp-edged side and a rounded-edge side (the difference is subtle). Place them with the sharp edge of
the washers facing up toward the knob, rounded edge down onto the painted surface of the base plate. If you install the
washers with the sharp edge down, they will bind into the paint and prevent smooth movement. If you do not have a
permanent installation, you may wish to mark the down side of the washer with a permanent marker so that you can quickly
identify the desired orientation.
1. The altitude axis should be fully locked down with a hex key before adjusting the azimuth.
17

2. Follow one of the methods of polar alignment mentioned above.
3. During the initial adjustment phase, the 4 lock-down knobs should be hand tight only. This will allow easy
movement of the azimuth axis.
4. When you are close to the final position of the azimuth axis, use a hex key to lock down the rear knob only. The
azimuth can still be moved with the adjusters, but it will now be solidly connected to the pier top. The other knobs
should remain hand-tight. The weight of the mount and scope puts pressure on the front of the plate for a solid
connection, so it is not necessary to lock them down fully with a hex key.
Altitude Adjustment
Loosen the altitude locking knobs. Move the polar axis up or down with the large altitude adjustment knob located in the front
of the polar axis assembly. The tommy bar can be positioned in any of the threaded holes located in the altitude adjustment
knob. Use this bar to help you turn the knob. Please refer to the illustrations on pages 7 and 8 if you are unsure about these
parts. It is also possible to make fine altitude adjustments by using the turnbuckle on the north leg of our pier, if used.
One full turn of the altitude knob is approximately 0.5 degrees (30 arc minutes).
Tips for Adjusting the Altitude
The mount's polar axis is held in place between the two side plates. It is possible for the mount to shift slightly when the side
bolts are fully tightened down after adjustment of the altitude angle. To prevent that, it is suggested that the initial altitude
adjustment be done with these bolts hand tight, and as you approach the final adjustment point, tighten the bolts with a hex
key after each movement. If you move the axis too high and overshoot the angle, it is better to loosen the two bolts a bit,
bring the axis back down a very small amount and progress back up with the bolts hand tight. This way you are using the
weight of the mount to insure a solid connection to the altitude adjuster. During the final adjustment phase, screw the Tommy
bar into one of the holes in the knob. This bar can then be used as fine adjustment tool and is a good indication of the
position of the axis.
18

Understanding the R.A. and Dec. Clutch Knobs
We suggest that you read this before assembling the remainder of your system.
1. What do they do?
The four R.A. and four Dec. clutch knobs depicted in the Assembly Diagram on page 6 have the function of
connecting the R.A. and Dec. axes to their respective drive worm wheel gears. Their function is progressive, from
no tension (axes free to move - as required during correct balancing of the telescope) to a completely "locked up"
state.
2. How can you find out what they really do?
As shipped, all 1200 mounts have all four R.A. and Dec. clutch knobs firmly hand tightened. This will give you a
good idea of the maximum tightness (clutch action) that can be achieved by hand effort alone. At this point, you
must bear in mind that for optimum performance all four clutch knobs on each axis (R.A. or Dec.) should be
tightened evenly with the same tension i.e. all four half tight, all four fully tight, etc.
In order to feel the effect of the clutch knobs, you may wish to partially assemble your mount. Fit together the R.A.
and Dec. assemblies plus mounting plate and counterweight shaft. Do not put scope and counterweights on at this
stage. With the above assembly (with the clutch knobs firmly hand tightened - "as shipped"), you can feel the
amount of force needed to move each axis by hand. Grab each end of the telescope mounting plate and move it
with a backward and forward movement of the Dec. axis. You will feel considerable resistance to this motion.
Perform the same operation on the R.A. axis by moving the counterweight shaft backward and forward. With a
well-balanced telescope, the above tightness of the clutch knobs will be sufficient for all normal conditions of use.
Now, if you proceed to mount up and balance your telescope, you can "feel" what this resistance in R.A. and Dec.
(movement backwards and forwards) is like when you make these motions from the eyepiece end of your
telescope as you would during normal use when slewing (pushing) by hand to acquire an astronomical object within
the field of view of your finder or scope.
3. How tight can the clutch be and can you do any damage by pushing against them?
The maximum tightness of this clutch system is 1/3 turn (with a 5/32 hex key) further in than the tension you can
achieve with the knobs by hand. You will see that each clutch knob has a 5/32 hex socket for tightening with a hex
key. With this extra 1/3 turn on each clutch knob, the axis (axes) will be considered completely "locked up" and you
should not attempt to push your scope by hand against this "locked up" resistance, or undue stress will be placed
on the worm wheel/worm and bearings.
However, if you are undertaking a very long astrophoto exposure, it is advisable to increase the pressure on each
clutch knob (with the 5/32 key) by about 1/8 turn past hand tight on Dec. and 1/8th turn past hand tight on R.A. You
may safely slew the scope by hand with this tension, however you will notice considerably more effort is required to
achieve movement. This is the absolute maximum tension that can be used for hand slewing. As a general rule, if
you have a big scope (7" or 8" refractor) with all the accessories, you will need more clutch tension than a 5" or 6"
scope.
WARNING! Resist the urge to over tighten the clutch knobs with the hex wrench. This will only cause them to
deform and lock into position. If you find that you are no longer able to adjust the tension and the knobs are locked
firmly in place so that the axis will not move, please refer to the Clutch Plug Replacement Section at the end of this
manual.
Balancing Your Telescope
For proper operation, the telescope must be adequately balanced along both axes. Start by balancing the tube assembly.
First, Balance the Declination Axis
1. Position the mount for balancing. Move the R.A. axis so that the counterweight shaft is pointing down. The
declination axis assembly will be in the meridian (this is the classic photographic pose for a German Equatorial).
Position the Dec. axis so the telescope tube is horizontal and pointing east.
2. Tighten the 4 R.A. axis clutch knobs.
3. Loosen the 4 Dec. axis clutch knobs (about 3/4 to 1 turn) so that the telescope moves freely about the declination
axis. Be careful because if your telescope is significantly out of balance, it may swing rapidly in the out-of-balance
direction!
19